1. Fields of the Invention
The present invention relates to a visual image sensor system which, in detecting an abnormal change in a picture monitored by a video camera, issues an alarm and transmits, if necessary, picture information via a telephone line after information compression. More particularly, the invention relates to a visual image sensor system in which the employment of artificial intelligence technique realizes proper judgment and minimizes the number of false alarms.
2. Description of the Prior Art
A conventional picture change detector system for detecting an intruder or another abnormal condition, such as disclosed in Japanese patent application No. 46791 of 1980 opened on Dec. 11, 1980 under Provisional Publication No. 159684/80, compares an input picture with a pre-set picture to issue an alarm when a difference between the two pictures is greater than a predetermined level. Said difference is evaluated by an averaged value and a maximum value of absolute differential values between picture signals of said two pictures in order to eliminate false detection caused by a noise. In this prior art, however, there is a drawback that normal changes which may occur in the input picture are not discriminated from actual abnormal changes to be detected. For instance, when a monitored region is set outdoors, the input picture monitored by a video camera must include changes in shaded portions, as the sun changes its position. Even if the monitored region is set indoors, the input picture must include changes in shaded portions when illumination is turned on or turned off. These changes, though they are not abnormal conditions, are detected as picture changes to issue false or redundant alarms in the conventional picture change detector.
Another type of picture change detector system, such as disclosed in U.S. Pat. No. 4,337,481, carries out scanning at two different rates in order to more reliably detect fast and slow motion in a scene being viewed. In this prior art, although the rate of the change is detected, directions or tracks of the change are not taken into consideration. Therefore, this prior art system cannot discriminate, for instance, a guest at an entrance from an illegal intruder through a window or over a fence, which also increases false or redundant alarms.